"If violence against women was taken seriously, the Sydney siege would never have happened."

It was morning when he approached the Lindt Cafe counter in Sydney’s Martin Place “nodding and smiling”. He asked to see the manager, Tori Johnson.

Man Monis had 43 sexual assault charges, a history of domestic violence and harassment.

He had been accused of being an accomplice to his wife’s murder.

Why was it fine that he was walking among us?

Eighteen people inside that Lindt cafe on December 15 2014 became his hostages.

It took police until 3pm to confirm Monis’s identity, as he forced those innocent people up against the glass windows of the cafe, their hands up, some of them holding Islamic State flags.

The 53-year-old’s history also came to light. That he came to Australia from Iran in 2004 under a protection visa. That he had recently pledged allegiance to ISIS.

That, in 2009, he’d been released on bail after being convicted of sending abusive and offensive messages to the families of vetran soldiers in the Middle East.

And then there were the details that might have provided a hint of the horror to come; the terror Monis had reigned over women, within his own workplace and home.

In 2001, Monis opened a “Spiritual Healing Practice” in western Sydney where he preyed on vulnerable women. Seven women sought out the help of lawyers after being sexually assaulted by their ‘spiritual leader’ Monis.

Twelve years later, Monis conspired to murder his ex wife – a 30-year-old woman and the mother of his three children. He tried hiring bikies to kill her but when that fell through, he enlisted the help of his new girlfriend – Greek-Australian woman Amirah Droudis who’d converted to Islam under Monis’ direction.

One day in April, while Monis took his children to the park and the swimming pool – taking care to film every movement with his phone as an alibi – Droudis lay in wait in the stairwell of his apartment. When his ex-wife returned to pick up the kids. Droudis stabbed her 18 times, doused her with petrol and set her alight. She was later sentenced to 44 years behind bars.

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Before he walked into the Lindt cafe that December morning, Monis had been charged with orchestrating the murder of his ex-wife, as well as 43 counts of sexual and indecent assault.

Twenty-two of those were for Aggravated Sexual Assault, which carries a maximum sentence of 20 years imprisonment in Australia.

One murder. 43 counts of sexual assault.

Why was it fine that he was walking among us?

The link between domestic violence and terrorism is not tenuous. The terrifying acts of religious extremism are highly visible on our television screens, our iPhones, compared with the secret, constant undercurrent of violence within the home.

Blink and you’ll miss the proven tendency for the perpetrators of domestic violence to escalate their crimes.

They might escalate to the murder of their partners – as was the case of Melbourne woman Kelly Thompson, 43, who was stabbed to death by her estranged partner in 2014.

They might escalate to the murder of their children – as was the case when 11-year-old Luke Batty was stabbed and beaten to death by his father after cricket practice, also in 2014.

In some cases, the perpetrators of domestic violence will escalate to the traumatisation of random strangers. Even acts of terror.

Tamerlan Tsarnaev, one of the men behind the Boston Marathon bombings, was also known to police for domestic violence and beating women.

Why was it fine that they were walking among us?

If domestic violence was taken seriously – by police, by psychologists, by the community – none of these men would have been free to cause 138 deaths, countless injuries, and a tidal wave of significant trauma between them.

Domestic Violence in Australia. Post continues below.

The Sydney Siege ended with two deaths: Katrina Dawson was a barrister, a wife and a mother of three. Tori Johnson, the manager at the Lindt cafe, who “would make you feel like the most important person in the room,” according to his mother.

The inquest into the event heard from the lead negotiator and a psychiatrist. Both men were heard claiming the Sydney siege could never have been predicted based on the history of violence from Monis.

The lead negotiator described Monis’ sex crimes as “passive, without anger or weapons” and the psychiatrist repeatedly used the words “acts of seduction” instead of “acts of sexual assault”.

These men were not the first to underestimate how dangerous Monis would turn out to be after his violence towards women.

And, if violence against women is not taken seriously in Australia, Monis won’t be the last of his kind to be underestimated.

How many more times will we have to ask: Why was it fine that they were walking among us?